Means for igniting propellant in rocket motors



Nov. 30, 1948.

H. W. MACE ETAL MEANS FOR IGNITING PROPELlI- IANT IN ROCKET MOTORS Filed Jan. 3. 1946 2 Sheets-Sheet l |NV T R5 25 HARRY G BBgI/ERLY H CHAMBERLAIN A TTORNEYS Nov. 30. 1948. w. MACE ETAL MEANS FOR IGNITING PROPELLANT IN ROCKET MOTORS Filed Jan. s. 1946 Y 2 Sheets-Sheet? INVENTORS HARRY (MACE lgEI/ERL Y H. CHAMBERLAIN ATTORNEYS Patented Nov. 30, 1948 MEANS FOR IGNITING PROPELLAN T IN ROCKET MOTORS Harry W. Mace, Glendale, and Beverly H. Chamberlain, Pasadena, Callh, assignors to Aerojet Engineering Corporation, Azusa, Call! a corporation of Delaware 1 Application January 3, 1946, Serial No. 638,742

l -Thls invention relates to jet propulsion and more particularly to means for igniting the propellant in a rocket motor.

The principal object of this invention'is to provide a simple and reliable means for creating ignition over a large surface of the propellant.

In the co-pending application of John W. Parsons, Serial No. 589,795, filed April 23, 1945, and assigned to the assignee as the present application, there is described and claimed an arrangement 'of the propellant substance in the combustion chamber of a rocket motor wherein so-called pans or receptacles are used to contain the propellant substance. The pans are preferably made v relatively flat and extend substantially throughout the length of the combustion chamber so that a large surface of the propellant is exposed for burning. It may sometimes be desired to use more than one pan for propellant in order to increase the effective burning area, inasmuch, as the propulsive thrust which may be generated by a rocket motor isdependent on the burning area.

It is a problem in -such a rocket motor to ignite the propellant, as it is desired that ignition shall take place over substantially the entire burning surface, practically instantaneously. According to our invention we create the desired ignition over the entire surface of the propellant by providing means for sending a heavy flame over all exposed propellant surfaces. We carry this out by providing within the chamber a charge of a readily combustible material such as black powder. This material may be arranged, for example, in the form of a flat disc or plate andplaced in a convenient position within the cham- 5 Claims. (Cl. 60-355) her so that it may receive the flame from an externally operated ignitor. The ignitor may be of any suitable form providing a local hot flame sufficient to ignite the combustible substance. While the flame from the ignitor would not be sufficient to extend overall surfaces of the propellant, the disc or plate of combustible substance will produce the desired flame over all the propellant surfaces.

Our invention will be better understood from the following detailed description and accompanying drawings of which:

Fig. 1 shows a longitudinal cross section of a Fig. 3 is a detail view of the construction of Fig. 1.

In the drawings there is shown a rocket motor. Ill comprising a cylindrical chamber portion ll terminating at one end in a. nozzle I! through which the exhaust gases escape. At the opposite end the cylindrical chamber is closed by a head member [3 threaded to the chamber. There-is placed within the chamber a pair of flats or con-. tainers i4 and l5 filled with a propellant substance of a type suitable for operating a rocket motor. A suitable propellant, for example, is a mixture of a fuel and an oxidizer for burning the fuel. The fuel may, for example, be an asphalt, and the oxidizer may be a substance such as potassium perchlorate finely divided and uniformly mixed throughout the asphalt. Such a mixture is a solid thermoplastic substance which can be poured into the pans or flats while hot and allowed to solidify while cooling. 7

The pans are placed back to back and may be fastened together by a fastener 25. In this way the propellant surfaces It andv I! are exposed. These surfaces I6 and I1 constitute the burning surfaces of the propellant and the burning should In order to ignite all parts of the propellant 7 surfaces simultaneously, we provide a disc of a highly inflammable material at the ends 'of the pans at the head end of the chamber. The disc may, for example, comprise a charge of ordinary black powder l8 encased by a wrapping 19 of cellulose nitrate. The attaching arrangement for the disc, shown lathe-drawings, comprises an asbestos sheet 20 placed over the ends of the pans;

. tapes 2| and 22.

To ignite the disc l9 we provide a suitable ignitor which will direct a hot flame against the disc when it is desired to set the motor into operation. The ignitor may be of a suitable form fitted through the center of the head [3 so that the flame will impinge on the disc. The ignitor may, for example, comprise a plug 23 fltted'through the head l3 and having fitted within its inside end a container 24 of black powder or theflike. Electric wires 25 passing through the plug connect with an igniting element such as a hot wire, to ignite the powder.

In operation it is only required to send electrical current through the ignition wire of the ignitor to set off the ignitor charge which directs its flame against disc l8. The material of the disc I8 is sufliciently inflammable to create a hot flame filling the spaces within the combustion chamber ll thereby producing sufllcient heat at surfaces i8 and I! to ignite the propellant.

Our invention is not limited to the particular form shown. For example, we may ignite any desired number of propellant surfaces such as one or more. The inflammable substance l8 may be of any suitable shape and need not necessarily be attached to the containers; as it is only required that it be placed in relation to the flame from the ignitor.

We claim:

1. In a rocket motor of the type having a tubular combustion chamber with a nozzle at one end of the chamber and the chamber being closed at the other end, a container containing propellant within the chamber with the exposed surface of the propellant facing the wall of the chamber, an inflammable substance placed at the end of the container adjacent the closed end of the chamber, and an ignitor placed through the closed end so that the heat from the ignitor ignites the inflammable substance causing flame to carry to the propellant surface.

2. Apparatus according to claim 1 in which the inflammable substance is contained within an inflammable envelope.

3. Apparatus according to claim 1 in which the inflammable substance is a powder placed within a disc-like envelope of inflammable material, said envelope being fastened to the end of the container.

4. In a rocket motor of the type comprising a combustion chamber which is closed except for an exhaust nozzle at one end of the chamber, a

container containing solid propellant within the chamber, the container having a side which covers the propellant and having an open side which leaves an exposed propellant surface facing a wall of the chamber, an inflammable substance attached to said covering side, and an ignitor placed through the chamber so that heat from the ignitorignites the inflammable substance, causing flame to carry to the exposed propellant surface.

5. In a rocket motor of the type comprising a combustion chamber which is closed except for an exhaust noz zle at one end of the chamber. a box containing solid propellant within the chamber, the box having sides which hold the propellant within them, there being some space between the sides and the inner wall of the chamber, the propellant having an exposed surface facing the chamber wall with space between the chamber wall and the surface, an inflammable substanceattached to one of the sides, and an ignitor placed through the chamber and arranged adjacent the substance so that heat from the ignitor ignites the inflammable substance, causing flame to carry to the exposed propellant surface.

HARRYWMACE, BEVERLY H. CHAMBERLAIN.

- REFERENCES crra The following references are of record in the flle of this patent:v

UNITED STATES PATENTS Number Name Date 2,395,435 Thompson et ai. Feb. '26, 1946 FOREIGN PATENTS Number Country Date 427,951 France June 10, 1911 831,496 France June '7, 1938 

